Biaxially stretched blow molded bottles made of Polyethylene Terephthalate (hereinafter, abbreviated as PET) are used in various fields, such as beverages, foods, cosmetics, and so forth. Especially, bottles for use in applications demanding a gas barrier property are made by laminating an intermediate layer made of a gas barrier resin, such as a nylon-based resin and an ethylene-vinyl alcohol copolymer, with substrate layers made of a PET resin as the main resin, in a manner such that the intermediate layer is embedded therebetween. Patent Literature 1 describes a process of molding a laminated preform, which is a primary molded product used in biaxial stretch blow molding of a laminated bottle in which an intermediate layer made of a nylon resin is laminated between substrate layers made of a PET resin.
In such biaxially stretched blow molded bottles, although the substrate layers are in tight contact with the intermediate layer, these two layers are in many cases not adhered to each other due to a difference in the materials. Accordingly, the two layers might be partially delaminated under the action of shearing force caused by an impact of dropping or the like. Once the partial delamination as described above occurs in the layers of a bottle used for, for example, a carbonated drink, carbon dioxide gas permeates an inner layer of the PET resin and enters the delaminated portion. The resulting pressure of carbon dioxide gas further exacerbates the delamination until the delamination is visible in external appearance when light is scattered or reflected from the delaminated interface, which ruins the appearance.
In this connection, the present inventors have proposed in Patent Literature 2 a laminated bottle by which the aforementioned problem of delamination in a bottle including an intermediate layer is solved. In detail, FIGS. 10A and 10B illustrate an exemplary bottle 201 according to Patent Literature 2, which includes a neck 202, a neck ring 203, a shoulder 204, a cylindrical body 205, and a bottom 206 having a “petaloid” shape with a plurality of extended feet. In the illustrated example, in a predetermined range extending from right below a lower end of the neck ring 203 to right above an upper end portion of the bottom 206, the bottle 201 has a laminar structure including an intermediate layer 213 (in a cross-hatched pattern) sandwiched between substrate layers 211, i.e., an outer layer 211a and an inner layer 211b. Furthermore, the intermediate layer 213 is segmented in the circumferential direction by vertical connecting zones 214 in which the outer layer 211a and the inner layer 211b are connected. According to the laminated bottle with the above structure, even when an impact due to dropping or the like causes the delamination in one of strips of the intermediate layer, the vertical connecting zones prevent progress of the delamination to adjacent strips. Restricting occurrence of the delamination to the limited strip allows the bottle to maintain its fine appearance and transparency.